1. Field of the Invention
The invention generally relates to electrical systems and devices. More specifically, the invention relates to a housing or mounting assembly with diverse electrical components, especially to electronic systems and devices. The invention relates to methods and apparatus for cushioning of a computer peripheral from mechanical shocks and vibrations, especially a memory unit peripheral such as a disk drive. The method and apparatus employ highly viscous fluids that flow readily at ordinary ambient temperatures, operative in a porous elastic structure.
2. Description of Related Art
including information disclosed under 37 CFR 1.97 and 1.98 The term “disk drives” may refer to any of several types of devices, including but not limited to hard disk dives, floppy disk drives, and optical disk dives such as CD and DVD drives. These disk drives share a common characteristic of having one or more rotating recording media disks, and having a transducer positioned over a surface of the media. Disk drives also share the characteristic of being highly susceptible to damage, in part due to external shock and vibration and in another part due to internally generated vibrations that are not sufficiently damped by the disk drive mounting.
A drive using fixed rotating disks inside it is called a fixed disk drive. A drive using removable disks enclosed in an envelope is called a removable media disk drive and the envelope containing the disks is called a removable disk cartridge. When the fixed disk drive itself is enclosed in an envelope and a shock resistant system is placed between them, then this assembly is called a removable drive module. A removable disk cartridge is removable from a disk drive while a removable drive module is removable from a docking device installed in a computer or an array chassis. Examples of removable disk cartridges include both industry standard floppy disk cartridges and removable hard disk cartridges. Floppy disk cartridges are supplied by many manufacturers. The 3.5-inch form factor designation does not necessarily refer to any dimension of a drive, itself. Rather, it refers to size of the disk that is designed to fit into the drive. Examples of removable disk cartridges include commercially available products supplied by companies such as lomega, Castlewood and SyQuest. DataZone Corporation of Felton, Calif., manufactures and sells a prior art removable drive module under the trademark, DataBook. The drive module can utilize an optical disk drive, a tape drive and other such drives besides hard, magnetic disk drives.
One application of the present invention relates to removable drive module technology. In known prior art, foam, polymeric material, mechanical springs or a combination of these materials and devices provide shock and vibration protection to a disk drive. The following patents show state-of-the-art damping schemes. However, these fall short of achieving shock protection to a level reaching 7,000 Gs. The present invention overcomes this limitation.
Prior art includes U.S. Pat. No. 6,351,374 to Sherry; U.S. Pat. No. 6,249,432 to Gamble et al.; U.S. Pat. No. 6,154,360 to Kaczeus Sr. et al.; U.S. Pat. No. 5,837,934 to Valavanis et al.; U.S. Pat. Nos. 4,638,383 and 4,568,988 to McGinlay et al., and U.S. Pat. No. 3,384,221 to Houtman. These patents provide limited teachings that refer only to foam materials, which do not achieve the desired degree of protection.
U.S. Pat. No. 6,154,360 to Kaczeus, Sr., et al. is assigned to DataZone Corporation. It shows a data storage subsystem that is capable of withstanding rough handling. A data storage device such as a hard disk drive is partially surrounded by a specially configured foam enclosure, formed, for example, of polyurethane foam. In turn, the foam enclosure and disk drive are encased within a shock resistant module housing, such as one formed of high impact plastic. Within the module housing, the foam enclosure surrounds the narrow periphery of the disk drive and supports both the top and the bottom broad surfaces of the disk drive. The module housing may be slotted for ventilation.
U.S. Pat. No. 6,249,432 to Gamble et al. discloses a removable hard disk drive mounted in a carrier or tray for insertion into a docking bay. A three-component vibration damping system reduces vibration between the hard disk drive and the carrier and between the carrier and the docking bay of a computer using such drives. One component is composed of polymeric material and is located between the exterior of the carrier and the interior of the docking bay. A second component of similar polymeric material is located between the interior of the carrier and the exterior of the hard disk drive with an interference fit. The third component employs metal or polymer springs and polymeric pads located between the exterior sides of the carrier and the interior sides of the docking bay. This patent relates only to disk drives and not to general packaging and protecting of objects and systems.
U.S. Pat. No. 6,351,374 to Sherry discloses a hard disk drive module having a protective cover housing or a modular case. The module uses insulator foam or other resilient material on one side or edge of the unit so as to maintain engagement with the other side or edge of a modular case. The resilient material can reduce shock to the disk drive unit due to impact on either the case or the chassis. Even a flexible cable leading to an electrical connector is attributed with the qualities of a shock absorber. Thus, this patent teaches a degree of shock absorption, but the extent of shock absorption appears to be low.
U.S. Pat. No. 5,837,934 to Valavanis et al. presents the use of foam sheets to provide shock absorption. It neither anticipates nor suggests applications for protecting other objects, systems, or devices by use of viscous means.
U.S. Pat. Nos. 4,638,383 and 4,568,988 to McGinlay et al. provide a prior art disk drive design. These patents teach an anti-vibration mount using an elastic rubber material known as AVM 206. The capability of such a mount material is 40 Gs of non-operating shock from the elastic deformation property of the material. The shock absorption of this class of elastic or rubber materials is very limited compared to what is required to address non-operating shocks reaching a level of 7,000 Gs. This patent does not suggest nor anticipate viscous means as an essential part to protect a disk drive from shock or vibration.
U.S. Pat. No. 3,384,221 to Houtman claims the invention of adding a plurality of fingers or cuts in foam padding used for shock protection. A package can be dropped from a maximum height of 76.2 cm (30 inches). Transmitted shock may be to 11 Gs. However, this patent neither suggests nor discloses the use of any viscous liquid for shock or vibration damping.
Additional prior art includes U.S. Pat. No. 6,347,411 to Darling; U.S. Pat. No. 6,339,532 to Boulay et al.; U.S. Pat. No. 6,039,299 to Ohnishi et al.; U.S. Pat. No. 5,995,365 to Broder et al.; U.S. Pat. No. 5,965,249 to Sutton et al.; and U.S. Pat. No. 5,510,954 to Wyler. These patents mention the use of viscous materials. However, they do not anticipate the methods and apparatus used in the present invention.
U.S. Pat. No. 6,347,411 to Darling discloses the use of viscous liquids and micro-balloons but does not present an interaction between a viscous liquid and an elastic, self-forming structure. Viscous liquid is used to dissipate energy within a closed cell material that entraps the liquid. The viscosity of the liquid is specified between 100,000 centistokes (cs) and 2,000,000 centistokes (cs). These very high viscosity fluids are characterized as solids that exhibit cold flow or creep. Various testing measures the characteristics of materials that cold flow or creep at low rates. The viscous fluids are encapsulated and entrapped within a cell to provide dissipation of shock energy at the microscopic and molecular level of the viscous fluid. In contrast, the present invention provides for dissipation of energy at the macroscopic level where liquid flows between cells of an internal structure and inside of an external membrane.
U.S. Pat. No. 6,339,532 to Boulay et al. discloses mounting a disk drive by a layer of viscoelastic material, such as double-sided foam tape, between the drive and an enclosure. Primary and secondary mounting plates may employ the viscoelastic material between them, and these plates should have aligned ventilation holes for cooling. This mounting controls internally and externally developed vibration relative to a disk drive but does not extend the performance capabilities to protect it from operating or non-operating shock. The viscoelastic material, sandwiched between two plates, dampens vibrations that may otherwise affect recording device performance or cause tracking errors. However, Boulay does not suggest the use of a viscous liquid for damping. Rather, a viscoelastic material in the form of a foam pad damps operational vibration but does not protect from shock. Further, the protective mounting primarily is effective during operation, when the device is mounted into an enclosure. Thus, Boulay does not envision protection of a device outside of the enclosure.
U.S. Pat. No. 6,039,299 to Ohnishi, et al. discloses a viscous damper for a disk-reproducing unit. The damper consists of a viscous fluid and two elastic cavities connected by a tube to a protuberant cavity. Damping occurs due to shear forces at irregular formations of both surfaces of the cavities and involves flow through the single orifice of the connecting tube. This technology is applied to a disk-reproducing unit that is always found in a manufacturing area. As such, it is not subject to the shock danger encountered by a portable device. This patent is readily distinguished from the present invention in that it does not suggest the use of an open celled material or a structure providing a multitude of orifices.
U.S. Pat. No. 5,995,365 to Broder, et al. teaches the use of flexible cables to reduce the transfer of shock forces among electronic components such as a motherboard and a hard drive-carrier assembly. The Broder patent also teaches a method of using articulated arms as shock absorbers. This teaching does not suggest an encapsulated viscous liquid that transfers to and from elastic open cells to dissipate shock and vibration. The energy dissipation is at a molecular level and not at a macroscopic level as envisioned in the present invention.
U.S. Pat. No. 5,965,249 to Sutton, et al. teaches a cold flowing material with high internal cohesion forces. This technology employs entrapment rather than flow of fluid between cells of porous material. Molecular level dissipation within the fluid produces damping. Cold flowing material produces only small displacements on a microscopic scale. It is unlikely that such materials can absorb shocks up 7,000 Gs.
U.S. Pat. No. 5,510,954 to Wyler teaches acoustic shielding. A key element is a fluid impervious barrier layer located next to sound absorptive porous foam. No liquid is located within the cells of the porous foam. A pouch contains liquid, but this liquid is separated from the foam layers by an impervious membrane of the pouch. The acoustic shielding employs no viscous liquid or porous elastic structure.
Various other patents show background art. U.S. Pat. No. 5,546,250 to Diel uses an elastomer seal to cover the frame of a drive and absorb external loads applied to the edges of the housing. The protection system is applied to a disk drive perimeter rather than to a module. U.S. Pat. No. 4,891,734 to More et al. shows the use of an elastomer body to encapsulate an electronic assembly that is confined in a closed cavity of a structure subject to vibration and shock. U.S. Pat. No. 5,216,582 to Russell et al. describes a housing assembly that forms a fixed disk drive module for a low profile fixed disk drive that is shock-mounted therein. Both More and Russell use elastomer supports to protect from shock and vibration.
As an example of the available technology in a current commercial product, the Maxtor XT 5000 external hard drive uses two plastic structures which cover four corners and two long edges of the case. The Maxtor 5000XT manual warns not to bump, jar, or drop the drive. The Maxtor specification for this drive is 250 G for linear shock.
Other literature references provide pertinent background. In a pioneering work, Dynamics of Package Cushioning, R. D. Mindlin describes the dynamics of package cushioning in terms of mathematical formulations. C. W. Radcliffe applies a viscous fluid damper to problems of prosthesis in Biomechanical Design of a Lower-Extremity Prosthesis. Specifically, a vane or a piston is used to move a viscous liquid from one chamber to another through a carefully designed orifice to effect a desired performance characteristic for a prosthetic knee mechanism.
Various commercial devices employ viscous liquids. For example, automobile shock absorbers operate with viscous liquids. Many industries use similar devices. They all have in common rigid chambers and orifices to hold the viscous fluid and control its flow.
Still other literature references show the importance of shock and vibration protection in the disk drive industry. See, for example, Stevens, L. D. et al: Magnetic Recording Technology; Chen and Kumano: The Efficacy of Mechanical Damper in Actuators for Rotating Memory Devices; Lilley, D. T.: The Discussion of Some Engineering Trade-offs in Winchester Disk Drive Isolation and Shock Protection; and The Effects of Shock & Vibration on Rigid Disk Drives, by ATASI Corporation.
The above prior art analysis contrasts the essential or often occurring elements of certain embodiments of the present innovation. The present invention comprises additional embodiments that may or may not include all the elements listed above. All observations provided herein are directed to optional aspects of the present invention and are in no way expressions of limitations to the full scope of the present invention.
Portable Data Storage—A minimum requirement for portability of disk drives is the ability to survive multiple drops from a height of 91.44 cm (36 inches)s onto a hard surface without damage to the drive. The current commercial market demonstrates difficulty in meeting this standard. DataZone Corporation is the only known supplier of a commercially available hard disk drive cartridge that has met this specification. The successful product uses a foam enclosure inside of a shock resistant housing. However, even this product suggests a difficulty. Whenever possible, a manufacturer conforms its product to a known form factor. The size of the DataZone cartridge housing is a little larger than that of the popular 3.5-inch form factor hard disk drive. Little, if any, protection against external shock is provided to a 3.5-inch form factor hard disk drive by using the DataZone module. The product is limited to the use of 3.0-inch form factor and smaller form factor hard disk drives.
Removable media can meet the minimum shock requirement for portability. Iomega, SyQuest and Castlewood have shipped hard disk drive devices using removable media. The hard disk is contained in a cartridge that is removable from the drive. This makes for data portability. The inherent problem with removable media for hard disk drives is that the media becomes contaminated and this contamination transfers to the transducer in the drive. To counter the effects of the contamination, the recording capacity of the media is relatively decreased and the reliability of the overall system is compromised.
Floppy disk, CD, and DVD are other removable media. These media are much less susceptible to contamination. However, the capacity of the recording media is 0.01% to 1.0% of the capacity of a comparable size hard disk drive. These low capacities limit the application and usefulness of the removable media disk drives. In addition, the large numbers of floppy disks, CDs, and DVDs, which are often needed and used, require a large and carefully cataloged library. This same information is better stored on a single hard disk drive that has electronic means for cataloging.
There is a need for a disk drive module that can withstand high G-shock and meet vibration specifications for commercial and personal use. These specifications define levels of shock and vibration that the device must safely and reliably withstand at a minimum.
Shipments of Disk Drives—There are design standards for common carrier shipments based upon size and weight of a container and whether the package is shipped on or off a pallet. Special shipping containers have to be designed to protect all shipments of disk drives. A percentage of common carrier shipments experience shocks in excess of the design standards, resulting in costly damage and possible loss of data. Individual disk drives are shipped in expensive and bulky boxes lined with foam or other bulky, shock absorbing, paper based material.
Environmental concerns and new laws require recycling of packing materials. Foam and other polymeric materials are extremely difficult to recycle. Secondary shipment costs of these packaging materials are high because they have to be used in large volumes for adequate protection of delicate peripherals or instruments.
There is a need for a disk drive module that can withstand high G-shock for shipment by common carriers, eliminating the need for the design of special and expensive shipping containers.
Disk Drive Mounting—Whether the hard disk drive is mounted as a single component in a system or as an array of many disk drives, the mounting design is crucial to obtaining optimum performance and enhanced reliability. Previous mounting schemes use foams, polymeric materials, viscoelastic materials, mechanical springs or a combination of these materials and devices to provide the required shock and vibration damping to the disk drive.
These previous mounting schemes either mount the drive to a solid member of a case that incorporates shock and vibration damping material or mount the drive in a cartridge or some type of module having shock and vibration isolation and damping. The cartridge or module is then attached to a solid member of the case, with or without damping materials.
The design requirements for these mounting schemes are becoming more critical because:
1) Disk drive rotational speeds are increasing. Typical rotational speeds for hard disk drives have increased from 5400 rpm to 7200 rpm, with some drives now rotating at 10,000 rpm and 15,000 rpm. Slight imbalances will result in large vibrations and/or large forces that will accelerate component wear and induce damage to the drive(s).
2) Larger dense arrays of disk drives require smaller individual contributions in vibration forces from each individual drive. The drives are all rotating at the same speed. Thus, the probability of exciting natural vibration frequencies between the elements of the array is high.
Building of systems incorporating hard disk drives requires careful handling of each and every hard disk drive. Currently, during the process of removal from the shipping container and installation into a system or system module, there is no significant protection afforded to the hard disk drive. Typically, this operation is done by unskilled labor, worldwide. The largest numbers of hard disk drive failures happen during this installation process.
There is a need for a disk drive module that can both protect the hard disk drive during system assembly and meet the vibration and shock requirements. This is irrespective of whether the system uses a single hard disk drive or an array of disk drives.
Commonality of Form Factor—The high volume production growth in the disk drive industry is supported by common form factors.
There are well-defined and worldwide acceptances of 3.5-inch, 3.0-inch, 2.5-inch, 1.8-inch, and 1.0-inch form factors. However, there is no accepted form factor for a hard disk drive module. Besides the DataZone ruggedized module form factor, there are other, un-ruggedized modules of different dimensions being offered by many companies. These modules are not interchangeable for numerous reasons, size being one of them.
At some point in time, a form factor for hard disk drive modules will be defined such that increased module manufacturing will lead to higher volumes and reduced costs. At this time, the maximum protection for shock and vibration within this fixed form factor will be a competitive advantage. The smallest form factor module of the present invention provides high G-shock protection to the 3.5-inch form factor hard disk drive, which is the largest form factor in high volume production.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the method and apparatus of this invention may comprise the following.